Poly-alpha-olefins containing a stabilizer composition



United States Patent US. Cl. 26045.8 2 Claims ABSTRACT OF THE DISCLOSURE A stabilizer composition for stabilizing polymeric materials, particularly polyolefins, comprising (A) a 2,6-dialkyl-p-cresol of the formula:

wherein R and R" each are alkyl radicals having 12 to 18 carbon atoms;

(B) a dialkyl thiodialkanoate of the formula:

wherein R is an alkyl radical having to 20 carbon atoms and n is 2 or 3; and

(C) a phenyl salicylate of the formula:

wherein each R is independently hydrogen or an alkyl radical having 1 to 22 carbon atoms;

with or without a dialkylpentaerythritol diphosphite.

DISCLOSURE This is a continuation-in-part of Ser. No. 218,519, filed Aug. 22, 1962, now abandoned.

This invention relates to normally solid poly-alphaolefins and to the problem of protecting them against oxidative degradation.

Normally solid polymers of alpha-olefins, generally referred to herein as poly-alpha-olefins, such as, for ex- 3,454,523 Patented July 8, 1969 "Ice ample, normally solid polyethylene, normally solid polypropylene and the like, are prone to oxidative degradation. This is particularly true at elevated temperatures, that is, at temperatures above 20 C. This degradation involves rupture of the polymer chains and formation of carbonyl (=C=O) groups. Evidence of such degradation in its early stages is the presence of peroxides. As this degradation progresses, articles and coatings containing these polymers at large concentrations tend to crack, become brittle, and lose tensile strength to the extent of mechanical failure.

Normally solid poly-alpha-olefins are commonly exposed to elevated temperatures in making useful compositions and articles out of resins containing them, and also in normal uses of some of these compositions and articles. Thus, such customary processing procedures as roll compounding, injection molding, extrusion and the like involve elevated temperatures. In such end uses as electrical insulation, protective coatings for electrical wire, plastic pipes for hot water and steam, and the like, elevated temperatures are frequently normally encountered. Hence, when normally solid poly-alpha-olefins and compositions containing them are subjected to these procedures and employed in such end uses, oxidative degradation of the poly-alpha-olefins takes place.

It is common practice, therefore, to incorporate into poly-alpha-olefins additives which have been found to function in ways which inhibit or suppress oxidative degradation of poly-alpha-olefins. These additives are broadly referred to as stabilizers. There is a need, however, for more effective stabilizers and combinations of stabilizers.

The poly-alpha-olefin stabilizer composition of this invention comprises a synergistic mixture of a 2,6-dialkylp-cresol in which each alkyl has 12 through 18 carbon atoms, a dialkyl thiodialkanoate and a phenylsalicylate. The synergistic mixture can also contain a dialkylpentaerythritoldiphosphite.

The 2,6-dialkyl-p-cresol is a compound according to the following general formula:

wherein R' and R" are alkyl radicals having from 12 to 18 carbon atoms. Typical of these 2,6-dialkyl-p-cresols are:

2,6-di (n-octadecyl) -p-cres0l 2,6-di l-methylheptadecyl) -p-cresol 2 l-methylheptadecyl -6 (n-dodecyl -p-cresol 2,6-didodecyl-p-cresol Relative concentration of the 2,6-dialkyl-p-creso1 in the synergistic mixture of this invention broadly is in a range from about 0.002 to about 99% by weight of the mixture, generally is in a range from about 0.05 to about 35 by weight of the mixture and preferably is in a range from about 0.08 to about 15% by weight of the mixture.

The dialkyl thiodialkanoate is a compound according to the following formula:

wherein R is an alkyl radical having at least 4 carbon atoms, generally 4-22 carbon atoms and preferably 8-18 carbon atoms, and n is an integer from 2 to 3. Examples of a dialkyl thiodialkanoate are:

dibutyl 3,3-thiodipropionate dihexyl 3,3'-thiodipropionate dioctyl 3,3'-thiodipropionate didecyl 3,3'-thiodipropionate dilauryl 3,3-thiodipropionate dimyristyl 3,3'-thiodipropionate dipentadecyl 3,3-thiodipropionate dioctadecyl 3,3-thiodipropionate dieicosyl 3,3'-thiodipropionate didocosanyl 3,3-thiodipropionate dibutyl 4,4'-thiodibutyrate dioctyl 4,4-thiodibutyrate dilauryl 4,4'-thiodibutyrate dipentadecyl 4,4'-thiodibutyrate dioctadecyl 4,4-thiodibutyrate didocosanyl 4,4-thiodibutyrate Relative concentration of the dialkyl thiodialkanoate in the synergistic mixture of this invention is broadly in a range from about 0.002 to about 99% by weight of the mixture, generally from about 0.05 to about 35% by Weight of the mixture and preferably from about 0.08 to about 15% by weight of the mixture.

The phenylsalicylate is a compound according to the following formula:

wherein each R is a member independently selected from the group consisting of the hydrogen radical and alkyl radicals having l-22 carbon atoms. Typical compounds of this formula include:

Concentration of the phenylsalicylate in the synergistic mixture of this invention is broadly in a range from about 0.002 to about 99% by Weight of the mixture, generally in a range from about 50 to about 95% by weight of the mixture and preferably from about 70 to about 90% by weight of the mixture.

The dialkylpentaerythritoldiphosphite Component in a 4 preferred embodiment of the synergistic mixture of this invention is a compound according to the formula:

CHz-O wherein each R is an alkyl radical having 10-22 carbon atoms. Typical examples of a dialkylpentaerythritold1- phosphite include:

didecylpentaerythritoldiphosphite didodeeylpentaerythritoldiphosphite dipentadecylpentaerythritoldiphosphite dioctadecylpentaerythritoldiphosphite didocasanylpentaerythritoldiphosphite Concentration of the dialkylpentaerythritoldiphosphite in this preferred embodiment of the synergistic mixture of this invention is broadly in a range from about 0.003 to about 99% by weight of the mixture, generally in a range from about 0.02 to about 35 by weight of the mixture and preferably from about 0.08 to about 15 by weight of the mixture.

The normally solid poly-alpha-olefin composition of this invention consists essentially of a normally solid resin portion and at an effective concentration the synergistic composition of this invention. The normally solid resin portion consists essentially of at least one normally solid, poly-alphaolefin polymer.

The normally solid, poly-alpha-olefin polymer is a polymer derived from an alpha-monoolefinic hydrocarbon having 2l0 carbon atoms. Such a polymer is provided by the normally solid homopolymers of alpha-monoolefinic hydrocarbons having generally 2-10 carbon atoms, preferably 2-6 carbon atoms and usually 2-4 carbon atoms. It is also provided by the normally solid copolymers (which include graft polymers, addition polymers, block polymers and the like) of alpha-monoolefinic hydrocarbons having generally 2-10 carbon atoms, preferably 2-6 carbon atoms and usually 2-4 carbon atoms, as well as of these alphamonoolefinic hydrocarbons and other compounds. Examples of a normally solid polymer derived from an alpha-monoolefinic hydrocarbon having 2-10 carbon atoms include the linear and branched, low density and high density, crystalline and amorphous, normally solid, homopolymers and copolymers of ethylene, propylene, butene-l, isobutylene, pentene-l, 2-methylpentene-l, 3-methylbutene-1, hexene-l, 3,3-dimethylbutene-l, heptene-l, octene-l, nonene-l, decene-l, 4-methylpentene-l, 4-methylhexene-1, S-ethylhexene-l, 6-methylheptene-l, 6-ethylheptene-l, styrene, allyl benzene and the like. Processes for preparing a normally solid polyalpha-olefin polymer are well known and described in detail in the prior art. See, for example, the US. patent, No. 2,153,553, to Fawcett et al., the US. patent, No. 2,912,- 429, to Cash and the US. patent, No. 2,917,500, to Hagemeyer et al. In general, a normally solid, poly-alphaolefin, is a thermoplastic material which at 20 C. is solid. It includes the so-called poly-alpha-olefin waxes which usually have average molecular weights in a range from about 3,000 to about 12,000.

The normally solid resin portion of the poly-alpha-olefin composition of this invention, in addition to at least one normally solid, poly-alpha-olefin polymer, can also comprise other polymeric components. Thus, it can comprise a normally solid polymer derived from another alpha-monoolefinic hydrocarbon having 2-10 carbon atoms. It can comprise a different kind of polymer, generally present as a physical property improver.

.Thenormally solid, poly-alpha-olefin compositions of this invention can also comprise other antioxidants, ultraviolet light inhibitors, anticorrosion additives, antistatic agents, foaming agents, plasticizers, pigments, Waxes, mold release agents, slip agents, fillers, extenders and the like 5 .6 including physical property improvers other than poly- Example 2.Polypropylene composition meric compounds.

Concentration of the synergistic mixture of this in- Components: Parts by weight vention in the poly-alpha-olefin composition in general Resin pOrtin depends on the degree of stabilization desired. This in Normally solid polypropylene 1000 turn depends upon processing conditions and subsequent Additives portionenvironmental conditions to which the poly-alpha-olefin 2,6-didoceyl-p-cresol 1 composition is intended to be exposed. In general, hoW- D l yl 3, '-thi0 ipr0pionate 1 ever, a concentration broadly in a range from about p-Tert-octylphenylsalicylate 0.1003 to about 40% by weight of the total poly-alpha- 10 oefin polymeric content of the composition, generally I in a range from about 0.03 to about 20% by weight of Example Polypropylene composltlon the total poly-alpha-olefin polymeric content of the com- Components; Parts by weight position and preferably in a range from about 0.03 to Resin porti0n about 12% by weight of the total poly-alpha-olefin poly- 15 Normally Solid polypropylene 1000 meric content of the composition is an effective concen- Additives Portion tration for most end uses of the compositions. Such a 2543i1 methy1heptadecy1) p c1-eso1 1 concentration amounts to a concentration of each of the .Dilauryl 3,3LthiodiProPionate 1 individual components of the synergistic mixture being p Tewoctylphenylsalicylate 10 broadly in a range from about 0.001 to about 10% by weight of the total poly-alpha-olefin polymeric content of the composition, generally in a range from about Example 4--P1yPrPy1ene composltlon 0.01 to about 5% by weight of the total poly-alphaolefin polymeric content of the composition and prefcomponfmts' Parts by Welght erably in a range from about 0.01 to about 3% by weight Resm Pomon of the total poly-alpha-olefin polymeric content of th N y Sohd Polypropylene 1000 composition. Preferred concentration for the 2,6-dialkyl- Add1t1vep.rt1n p-cresol and dialkyl thiodialkanoate is 0.001 to 1% and 2.6'b1S(l'mefhylhelitadecyl)'p'cresol 1 for the phenylsalicylate 0.001 to 2%. Dllauryl 4,4 'thwdlblltyrate 1 The normally solid, poly-alpha-olefin composition of p'Tert'octylphenylsahcylate 10 this invention is prepared by incorporating the components of the synergistic mixture, either in admixture or Example 5.-Polypropylene composition individually, into the normally solid, resin portion of the. composition. Generally, such incorporation is performed mp nents: Parts by weight by any one of a number of known methods, such as roll Resin P compounding, extrusion, solvent mixing and the like. Normally solid polypropylene '1000 'For example, such incorporation can be performed by Additives P0fti0Il heating or otherwise softening the normally solid resin -m hylhepta ecyl)-p-creso1 1 portion to a workable consistency and then working in, Dilauryl 3,3'-thiodipropionate 1 as by roll compounding, the individual components of p-Octadecylphenylsalicylate 10 the synergistic mixture until a substantially uniform blend or dispersion is obtained. Generally, such incorporation takes place at the same time that other additives are nor- Example Polypropylene composltlon mally incorporated into the resin portion of the compo- Components; Pal-ts by Weight sition and usually along with such other additives as the 5 Resin Portion particular poly-alph-olefin composition formulation may Normally solid polypropylene 1000 require. Additives portion- The poly-alpha-olefin composition of this invention 2543il methylheptadecyl) p creso1 Y 1 is useful in coatings and as a material of construction Dilam-yl 3,3'4hiodiProPionate 1 for shaped articles. Thus, the composition can be made pgrert 0cty1pheny1sa1icy1ate 10 into various shaped articles such as, for example, Distearylpentael-ythritoldiphoSphite 1 pellets, sheeting, films, bars, tubes, filaments, fibers, specially shaped structural elements and the like as by conventional casting and molding techniques which in- Example 7.Polypropylene composition elude extrusions, blow-molding and the like.

This invention is further illustrated by the following Components 0 Parts y Weight examples of various aspects thereof, including preferred Resln P specific embodiments of the invention. This invention is N fi Polypropylene 1000 not limited to the specific embodiments unless otherwise Addltlves,portlon indicated 2,6-b1s(1-methylheptadecyl)-p-cresol 1 Dilauryl 3,3-thiodiopropionate 1 Specific embodiments of the poly-alpha-olefin compop octadecylphenylsaficylate 10 sition of this invention are formulated as follows: Distearylpentaerythritoldiphosphite 1 Example l.-Polypropylene composition Example 8' P1yPrpy,1ene composmon Components: Parts by weight Components: 'Parts by weight Re'sin portio Resin portion- Nonmally solid polypropylene 1000 Normally solid polypropylene 1000 Additives portion- Additives portion 2,6-didodecyl-p-cresol 1 2,6-di(tert-butyl)-p-creso1 1 Di'lauryl 3,3'-thiodipropionate 1 Lilauryl 3,3-thiodipropionate 3 p-Tert-octylphenylsalicylate 10 p-Tert-octylphenylsalicylate 10 Distearylpentaerythritoldiphosphite 1 Example 9.Poly(butene-l) composition Components: Parts by weight Re'sin portion Normally solid poly(butene'-1) 1000 Additives portion 2,6-bis(1-methylheptadecyl)-p-cresol 0.5 Dilauryl 3,3-th iodipropionate 1 p-Tert-octylphenylsalicylate 10 Example 10.-Poly butene-l composition Components: Parts by weight Resin portion Normally solid po-ly('butene-1) 1000 Additives portion- 2, 6-bis( l-methylheptadecyl)-p-cresol 0.5 Dilauryl 3,3'thiodiproprionate 1 p-Tert-octylphenyl -tert-butylsalicylate Example ll.Poly(butene-1) composition Components: Parts by Weight Resin portion Normally solid poly(butene-1) 1000 Additives portion 2,6-bis l-methylheptadecyl -p-cresol 0.5 Dilauryl 3,3'-thiodipropionate 1 p-Tert-octylphenylsalicylate 10 Distearylpentaerythritoldiphosphite 1 Example 12.-Propylene-butene-1 copolymer composition Components: Parts by weight Resin portion Normally solid copolymer of propylene and butene-l, the weight ratio of propylene content to butene-l content being 90:1 1000 Additives portion .2,6-bis( l-methylheptadecyl)-p-cresol 0.5

Dilauryl 3,3'-thiodiproprionate 1 p-Tert-octylphenylsalicylate 10 Example 13.Propylene-butene-l copolymer composition Components: Parts by weight Resin portion Normally solid copolymer of propylene and butene-l, the weight ratio of propylene content to butene-l content being 90:1 1000 Additives portion 2,6-bis( l-methylheptadecyl -p-cresol 0.5 Dilauryl 3,3-thiodipropionate 1 p-Tertoctylphenylsalicylate 10 Distearylpentaerythritoldiphosphite 1 Example 14.Propylene-isoprene polyallomer composition Components: Parts by weight Resin portion- Normally solid propylene-isoprene polyallomer, the weight ratio of propylene content to isoprene content being 1000:7 1000 Additives portion- 2,6-bis(l-methylheptadecyl)-p-cresol 0.5

Dilauryl 3,3'-thiodipropionate 1 p-Tert-octylphenylsalicylate 10 The propylene-isoprene polyallomer called for in the formulation of this example and in the formulation of the following example is a normally solid, crystalline polymer made as by first polymerizing propylene to form a crystalline, propylene polymer and then copolymerizing said propylene polymer with isoprene until the resulting product has an isoprene content of about 0.7% by weight.

Parts by weight 2,6-bis( l-methylheptadecyl)p-cresol 0.5 Dilauryl 3,3 '-thiodipropionate 1 p-Tert-octylphenylsalicylate 10 Distearylpentaerythritoldiphosphite 1 The specific compositions of the foregoing formulations are each prepared by banding the resin portion of the composition on hot milling rolls, the temperature of the front roll being at 330 F. and the temperature of the rear roll being at 280 F. As soon as the resin portion has reached a workable consistency, the components of the additives portion of the formulations are then added to the resin portion on the rolls and milled thereby into the resin portion. Addition of the additives portion is as rapid as possible so as to keep the total milling time to a total of about six minutes. At the end of this time, the resulting poly-alpha-olefin composition is stripped from the rolls and then granulated. If desired, the granulated composition is then cast, molded or extruded into the desired article.

The stabilities of these specific, poly-alpha-olefin resin compositions of this invention, and thus the stability of the general poly-alpha-olefin composition of this invention, relative to oxidative degradation, are demonstrated by the following tabulated test data obtained in the stability testing of these and other poly-alpha-olefin compositions. The stability test and procedure thereof employed in this testing are as follows:

160 C. Oven Life Test.-In this test, 0.25 gram specimens /2 inch by /2 inch by inch) are cut from a compression molded plate (8 inches by 8 inches by inch) of the sample, and placed on separate 25 millimeter watch glasses. These specimens are stored in a forced air oven at a temperature of 160 C. Periodically, one of the specimens is removed and analyzed as follows for the presence of peroxides.

The specimen is cut into 6-10 pieces and transferred to a 250 milliliter flask containing 20 milliliters of carbon tetrachloride. The pieces are digested in the carbon tetrachloride for 25 minutes over a steam bath and with frequent agitation. This aids the extraction of peroxides from the pieces since the resin portion of the pieces is not soluble in carbon tetrachloride. To the flask are then added 20 milliliters of a mixture of glacial acetic acid and chloroform at a volumetric ratio of glacial acetic acid to chloroform of 3:2, and 1 milliliter of saturated, aqueous, potassium iodide. The flask is stoppered and agitated for 2 minutes in subdued light. To the resulting reaction mixture in the flask are added milliliters of distilled water. One milliliter of starch is added as a color indicator for iodine which is liberated by the peroxides. The presence of peroxides is indicated by the mixture having a blue color.

As soon as a blue color is detected upon analysis of one of the specimens, the time is noted. The time interval in hours during which specimens of the test sample were in the oven is then determined. This time interval is the 160 C. oven life of the sample.

Table I summarizes the formulation and stability test data of test samples of various polypropylene compositions. The polypropylene used in making up these samples was a commercially available, normally solid, polypropylene characterized by a density of 0.91, an I.V. at C. of 1.96 and molecular weight greater than 15,000. The test samples were prepared by the procedure described in connection with, and following, the examples.

TABLE I Additive Concentrations In percent by wt. of Poly- No. Additives alpharolefin Dilauryl 3,3-thiodipropionate p-Tert-octylphenylsalicylate 9 2,6didodecyl-p-cresol 10 {2,tfrdidodecyl-p-creso1 Dilauryl 3,3-th1odipropionate 11 {2,6-didodecyl-p-cresol p-Tert-octylphenylsalicylate 12 {2,6-didodecyl-peresol- Dilauryl 3,3-thiodipropionate p-Tert-octylphenylsalieylate 13 2,6bis(1-methylheptadecyl) -p- 4 is -me y ep a eey -p- 14.. cresol. 170

Dilauryl 3,3-thiodipropionate 16 {2,6-bis(l-methylheptadeeyD-pcresol. p-Tert-octyphenylsalicylate. 2,6-bis(I-methylheptadecyD-p- Cl'es 16 Dilauryl3,3-thiodipropionate 240 p-Tert-octylphenylsalicylate Dilauryl 4,4-thiodibutyrate- 2,6-bis (l-methylheptadeeyD-pcresol. Dilauryl 4,4-thiodibutyrate p-Tert-o etylphenylsalicylate. 19 p-Octadecylphenylsalieylate... 20 2, 6-bis(1-methylheptade cyl) -pcresol. 17

p-Octadecylphenylsalicylate.. 2,6-bis(l-methylheptadecyl)-pcresol. Dilauryl 3,3-thiodipropionate p-Octadecylphenylsalieylate. Distearylpentaerythritoldiphosphite. 2,6bis(1-methylheptadecyl)-pcresol. Distearylpentaerythritoldiphosphite. 24 {Dilauryl 3,3-thiodipropionate.

Distearylpentaerythritoldiphosphite.

p-Tert-octylphenyl-salicylate Distearylpentaerythritoldiphosphite. 2,fi-bisq-methylheptadeeyl)-pcres Dilauryl 3,3-thiodipropionate Distearylpentaerythritoldip osphite. 2,6-bis(l-methylheptadecyl)-pcresol. p-Tert-octylphenyl-sallcylate. Distearylpentaerythritoldip osphite. 2,6-bis(I-methylheptadecyl) -pcresol. Dilauryl 3,3-thiodlpropionate p-Tert-octylphenyl-salicylate Distearylpentaerythritoldiphosphite. 2,6-bis (l-methylheptadecyl) -pcresol. Dilauryl 3,3-thio dipropionate. p-O ctadecylphenyl-salicylate. Distearylpentaerythritoldiphosphite. 2,6-didodecyl-p-cresol Dilauryl 3,3-thiodipropionate 0. 1

p-Tert-octylphenyl-salicylate. 1

Distearylpentaerythritoldi- 0. 1

phosphite.

Samples 8, 12, 16, 18, 21, 28, 29 and 30 in Table I correspond in formulation to the compositions of Examples 18, respectively.

These data of Table I demonstrate the outstanding effectiveness of the specific embodiments of the synergistic mixture of this invention in stabilizing polypropylene and thus poly-alpha-olefins generally, as compared to the individual components in these embodiments of the mixture and to other combinations of these components. In particular, these data of Table I illustrate the synergism of the components of the synergistic mixture of this invention. Stability after more than a certain number of hours, e.g., 240 hours, indicates that the composition of the invention was still stable when the test was terminated after a standard period. These compositions apparently exhibit stability substantially greater than normally measured in standard test periods.

Table H summarizes the formulation and testing stability data of test samples of various poly(butene-1) compositions. The poly(butene-1) resin used in each sample was from a batch of a normally solid poly- (butene-l) characterized by a density of 0.91, an IV. at 145 C. of 1.9 and molecular weight greater than 15,000.

These test samples were prepared by the general procedure of the examples.

TABLE II Additive Concentrations in percent: by

w Poly-alpharolefin Oven Sample Life In No. Additives Hours cresol.

Dilauryl 3,3-thiodiprop1onate 0. 1 2,6-bis(l-methylheptadecyD-p- 5 4 cresol.

Dilauryl 3,3 -thiodipropionate 0. 1

5 p-Tert-octylphenylsalicylate 1 2,6-bis(1-methylheptadecyl)-p- 6 cresol.

p-Tert-octylphenylsalicylate 1 7 {Dilauryl 3,3-thiodipropionate 1 p-Tert-octylphenylsalicylate 1 {iii-bis (l-methylheptadecyl) -p- 5 Distearylpentaerythritoldi- 4 phosphite. 13 {p-Tert-octylphenylsalicylate Distearylpentaerythritoldi- 0. 6

phosphite. 2, 6-bis(1-methylheptadceyl) p-eresol. p-Tert-o ctylphenylsalicylate. 1 Distearylpentaerythritoldiphosphite. 2,6-bis(l-methylheptadecyl) p-cresol. Dilauryl 3,3-thiodipropionate.. p-Tert-o ctylphenylsalcylate. l Distearylpentaerythritoldi- 0. 1

phosphite In Table II samples 8, 10 and 15 correspond in formulation to the compositions of Examples 9-12, respectively.

The test data of Table II demonstrate the outstanding effectiveness of the specific embodiments of the synergistic mixture of this invention in stabilizing poly(butene-1) and thus poly-alpha-olefins generally. In addition, the data of Table II demonstrate the synergism of the components of the synergistic mixture of this invention.

Table III summarizes the formulation and stability testing data of test samples of various propylene-butene-l copolymer compositions. Samples of these compositions were prepared in accordance with the general procedure of the foregoing examples, from a batch of propylenebutene-l copolymer characterized by a weight ratio of propylene content to butene-l content of :1, a density of 0.91, an IV. at C. of 2.6 and a molecular weight of the copolymer greater than 15 ,000.

TABLE III Additive Con- 160 C. centrations in Oven percent by wt. Life In Sample of Poly-alpha. Hours No. Additives olefin 1 N one 0. 2 2 2, dblsSl-methylheptadecyl)-p- 0. O 15 creso 3 Dilauryl 3,3'-thiodipropionate 0.1 2 4 p-Tert-octylphenylsalicylate 1 3 2, 6-bis(1-methylheptadecyl)-p- 0. 05 5 cresol. 150 Dilauryl 3, 3-tl1iodipr0pionato 0.1 6 {Dilauryl 3, 3-thiodipropionate. 0.1 5

p-Tert-octylphenylsalieylate 1 2, 6-bis(1-methylheptadecyl)-p- 0. 05 7 cresol. Q Dilauryl 3, 3-tl1iodipropionate 0. 1

p-Tert-octylphenylsalieylate. 1 8 Distearylpentaerythritoldi- 0. 1 5

phosphite. 2, 6-bis(l-methylheptadecyl)-p- 0. 05

cresol. 9 Dilauryl 3, 3-thiodipropionate- 0.1 240 p-Tert-oetylphenylsalioylate. 1 Distearylpentaerythritoldi- 0. 1

phosphite.

Samples 7 and 9 of Table III correspond in formulation to the specific compositions of Examples 12 and 13, respectively. The data of this table demonstrate the outstanding effectiveness of specific embodiments of the synergistic mixture of this invention in stabilizing a polyalpha-olefin. In particular, these data demonstrate synergism in poly-alpha-olefin stabilization on the part of the components of the synergistic mixture of this invention.

Table IV summarizes the formulation and stability testing data of test samples of various propylene-isoprene polyallomer compositions. The propylene-isoprene polyallomer compositions were prepared in accordance with the general procedure of the examples from a batch of propylene-isoprene polyallomer having a propylene content of 99.3% by weight, an isoprene content of 0.7% by weight, a density of 0.91, an IV. at 145 C. of 1.8 and molecular weight greater than 15,000.

TABLE IV Additive Concentrations 160 C In percent Oven Sample by wt. of Poly- Life In No. Additives alpharolefin Hours 1 None 0. 3 2 2, d-bisgl-methylheptadecyl)-p- 0. 05 15 creso 3 Dilauryl 3, 3-thiodiproprionate 0. 1 2 4 p-Tert-oetylphenylsalieylate 1 3 2, 6-bis(1-methylheptadeeyl)-p- 0. 05 5. cresol. 160 Dilauryl 3, 3-thiodipropionate 0.1 6 {Dilauryl 3, 3-thiodipropionate 0. 1 5

p-Tert-oetylphenylsalicylate 1 2, 6-bis(l-methylheptadecyl)-p- 0. 05 7 eresol. 235

Dilauryl 3, 3-thiodipropionate 0. 1 p-T ert-o cytlphenylsalicylate 1 8 Distearylpentaerythritoldi- 0. 1 5

phosphite. 2, 6-bis(l-methylheptadecyD-p- 0. 05

oresol. 9 Dilauryl 3, 3-thiodipropionate. 0. 1 965 p-Tert-Oetylphenylsalicylate--.. 1

Distearylpentaerythritoldi- 0. 1

phosphito.

Samples 7 and 9 of Table IV correspond in formulation to the specific compositions of Examples 14 and 15, respectively. The data of Table IV also demonstrate the outstanding effectiveness of specific embodiments of the synergistic mixture of this invention. These data likewise demonstrate the synergism involved in stabilizing a polyalpha-olefin by the synergistic mixture of this invention.

Thus, there is provided a new stabilizer composition which is especially useful for poly-alpha-olefins. A feature of advantage of the stabilizer mixture of this invention is that in poly-alpha-olefin compositions, it exhibits negligible discoloration. Still another feature of advantage of the stabilizer mixture of this invention is its effectiveness as an ultraviolet light inhibitor for polyalpha-olefins.

In addition, there is provided a new poly-alpha-olefin composition having an outstanding degree of protection relative to oxidative degradation.

Other features, advantages and embodiments of this invention will occur to those in the exercise of ordinary skill in the art upon reading the foregoing disclosure. In this regard, while this invention has been described in considerable detail relative to specific embodiments thereof, variations and modifications of these embodiments can be eifected within the spirit and scope of the invention as disclosed and claimed.

I claim:

1. A poly-u-olefin composition comprising polypropylene and a stabilizing amount of a synergistic stabilizer combination of 2,6-bis(l-methylheptadecyl)-pcresol, p-tert.-octylphenylsalicylate and a compound selected from the group consisting of distearylthiodipropionate and dilaurylthiodipropionate.

2. A poly-u-olefin composition according to claim 1 wherein distearyl pentaerythritoldiphosphite is additionally included in said stabilizer combination.

References Cited Derwent: Belgian Patents Report, vol. 1, No. 1, published May 1-15, 1961. Pertinent page: page A6, Belgian Patent 599,358 to Eastman Kodak Co.

DONALD E. CZAJA, Primary Examiner.

H. E. TAYLOR, JR., Assistant Examiner.

U.S. Cl. X.R. 

